Barrier packaged containers, otherwise known as barrier packs, were developed as a way of separating the propellant from the product to be dispensed. Placing a bag within the can also provided an expedient way of separating the product from the aluminum container. The bag was therefore directly connected to the valve mechanism, so that the contained product could be dispensed without contacting aluminum. Bi-compartmented aerosols became a way of dispensing products free of the contaminating effects of propellants, which remained trapped outside of the compressed bag within the container.
Barrier pack containers became popular due in part to the ability to dispense product without inadvertent expenditure of propellant when tilted in non-vertical positions. Since the flowable or sprayable product is kept in contact with the dispensing valve assembly, there is less chance that product will dry or crystallize in an air gap and thereby plug the valve assembly orifice.
Along with advantages afforded by the barrier pack, however, are several disadvantages. Bags must be carefully designed and constructed for purposes of manufacture, impermeability, immunity from rupture, and ease and completeness of product expulsion. Achieving a combination of these and other desired features remains difficult. For example, fabricating a thin bag from polyethylene often means that the bag, while facilitating ease of product expulsion, may permit the propellant to permeate the bag and contaminate the product; or the bag may fold up on itself and cause blockage of product.
With respect to these concerns, U.S. Pat. Nos. 3,240,394 and 3,433,391 disclose a dispensing container comprising a collapsible inner bag of plastic material having pleats to provide an orderly collapse near the top-mounted valve assembly and to avoid blockage due to folding of the material, or "panelling." Such a design, however, involves unnecessary complexity and added expense. The pleated structure and the amassing of the thick plastic material near the top of the outer container also hinder complete product expulsion.
Laminated containers have been used for products that are manually squeezed out of single-chambered containers, but such a design involving a laminated container has not been considered or treated in the context of barrier pack containers. The tubular body portions of prior art laminated containers have typically been produced by forming a flat laminate into tubular form and heat-sealing the edges to provide a tube having a longitudinal seam. Such a heat-sealed construction necessitates heat sealing compatibility of the inner and outer layers of the laminate and thus requires both layers to be thermoplastic. Such previous methods of construction thus limit the selectivity of materials and, consequently, the use of containers employing such body constructions. Moreover, the compatibility requirements for heat sealing have made it impossible to employ thermosetting plastic materials for the inner surface of the tubular body so as to minimize product permeation.
A laminated tube for collapsible containers and a method for making such a tube has been disclosed in U.S. Pat. No. 4,226,337 and Canadian Patent No. 1,153,321, incorporated herein by reference. The laminated tube disclosed in those references avoids many of the problems of conventional heat-sealed laminated containers. The purpose of the container disclosed therein, however, is to dispense products by hand squeezing and not by the use of propellants.
A product dispensing container is therefore needed having an inner laminated barrier tube that provides for sufficiently complete and efficient expulsion of product; that provides an inexpensive design for manufacture and assembly; that affords a high degree of impermeability between product and propellant; that prevents contamination of the product; that lends sufficient resistance to rupture; that provides a strong seal between outer aluminum container, valve assembly top, and inner barrier container; and that does not waste container volume through use of thick materials or bulky construction.